Late decaying 2-component dark matter scenario as an explanation of the AMS-02 positron excess

2016/09/30 by Jatan Buch, Pranjal Ralegankar, Vikram Rentala · 20 citations
Physics and Astronomy · #Annihilation #Astrophysics #Axion #Cosmic microwave background #Cosmology #Cosmology and Gravitation Theories #Dark Matter and Cosmic Phenomena #Dark energy #Dark fluid #Dark matter #Electron #Hot dark matter #Nuclear physics #Particle physics #Particle physics theoretical and experimental studies #Physics #Positron #Quantum mechanics #Scalar field dark matter #Universe #Warm dark matter #astro-ph.CO #astro-ph.HE #hep-ph

paper · pdf · doi:10.1088/1475-7516/2017/10/028

published in Journal of Cosmology and Astroparticle Physics 2017(10), 028 (Institute of Physics) · 34 pages, 4 figures. Matches journal version. 4$μ$ results emphasized

openalex created_date 2016/09/30 · openalex publication_date 2017/10/19 · arxiv created 2017/12/11 · arxiv updated 2017/12/12 · openalex updated_date 2026/08/05

Abstract

The long standing anomaly in the positron flux as measured by the PAMELA and AMS-02 experiments could potentially be explained by dark matter (DM) annihilations. This scenario typically requires a large "boost factor" to be consistent with a thermal relic dark matter candidate produced via freeze-out. However, such an explanation is disfavored by constraints from CMB observations on energy deposition during the epoch of recombination. We discuss a scenario called late-decaying two-component dark matter (LD2DM), where the entire DM consists of two semi-degenerate species. Within this framework, the heavier species is produced as a thermal relic in the early universe and decays to the lighter species over cosmological timescales. Consequently, the lighter species becomes the DM which populates the universe today. We show that annihilation of the lighter DM species with an enhanced cross-section, produced via such a non-thermal mechanism, can explain the observed AMS-02 positron flux while avoiding CMB constraints. The observed DM relic density can be correctly reproduced as well with simple s -wave annihilation cross-sections. We demonstrate that the scenario is safe from CMB constraints on late-time energy depositions during the cosmic "dark ages". Interestingly, structure formation constraints force us to consider small mass splittings between the two dark matter species. We explore possible cosmological and particle physics signatures in a toy model that realizes this scenario.

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